Ultra DMA CRC error rate Low value of this attribute typically indicates that something is wrong with the connectors and/or cables. Disk-to-host transfers are protected by CRC error detection code when Ultra-DMA 66 or 100 is used. So if the data gets garbled between the disk and the host machine, the receiving controller senses this and the retransmission is initiated. Such a situation is called "UDMA CRC error". Once the problem is rectified (typically by replacing a cable), the attribute value returns to the normal levels pretty quick.